fix: stackoverflow on circular importassets (#2666)

Fixes #2666

libsrc/ffdec_lib/src/com/jpexs/decompiler/flash/SWF.java

@@ -2421,7 +2421,11 @@ public final class SWF implements SWFContainerItem, Timelined, Openable {
                 if (importedSwfs.containsKey(url)) {
                     iSwf = importedSwfs.get(url);
                 } else {
-                    iSwf = resolver.resolveUrl(this.file, url);
+                    if (resolver.doIgnoreUrl(this.file, url)) {
+                        iSwf = null;
+                    } else {
+                        iSwf = resolver.resolveUrl(this.file, url);
+                    }
                     importedSwfs.put(url, iSwf);
                 }
                 if (iSwf != null) {

libsrc/ffdec_lib/src/com/jpexs/decompiler/flash/UrlResolver.java

@@ -16,6 +16,8 @@
  */
 package com.jpexs.decompiler.flash;
 
+import java.util.Stack;
+
 /**
  * URL resolver interface.
  *
@@ -31,4 +33,12 @@ public interface UrlResolver {
      * @return SWF object or null if not valid
      */
     public SWF resolveUrl(String basePath, String url);
+            
+    /**
+     * Check whether to ignore this url
+     * @param basePath Base SWF path
+     * @param url URL    
+     * @return True on ignore
+     */
+    public boolean doIgnoreUrl(String basePath, String url);
 }